A cylindrical battery such as a lithium ion secondary battery includes: a bottomed cylindrical battery case; an electrode group stored together with an electrolyte in the battery case; a disk-like sealing member for sealing an opening of the battery case; and an annular gasket interposed between the opening of the battery case and the sealing member. A drawing process is applied to the opening of the battery case. Thus, the gasket is compressed, and the sealing member is fixed to the opening of the battery case.
Specifically, by applying the drawing process to the opening of the battery case, the opening end of the battery case is bent or curved toward the center axis of the battery case, and an annularly extending constriction is formed around the center axis in the battery case. The gasket is compressed by the opening end and the constriction, and the rim portion of the sealing member is grasped by the compressed gasket.
Conventionally, in order to prevent the battery case from breaking due to the increase in internal pressure of the cylindrical battery, a pressure reducing mechanism such as a pressure reducing valve is disposed in the sealing member. Furthermore, in order to make the pressure reducing mechanism sufficiently exhibit its pressure reducing capability, the sealing member is firmly fixed to the battery case (Patent Literature 1 or 2, for example).